根据要求，解答下列问题．

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1.每处错误及其修改均仅限一词；2.只允许修改10处，多者（从第11处起）不计分。

    I was sitting at my favorite table in a restaurant on last Sunday waiting for the food I had ordered to arrive. I suddenly found that Lin Ling, one of my classmate, worked as a waitress there. Honest speaking, it was great surprise for me to find her working there. As far as I know, she's from a richer family. What made her work there? I walked up to her but asked her the reason. When asking, she said, “I just want to earn some pocket money so that we can help some children in poor areas go back to school.” How a good girl! I should learn from her.

下列各组混合物，使用氢氧化钠溶液和盐酸两种试剂不能分离的是（  ）